Windows are typically provided with screen assemblies fitted to the inside of the frame of the window opening, typically fixed to the upper face of the window opening or between the sides of the window opening adjacent the upper face thereof, for selectively obscuring the window. In the case of a roller blind, such screen assemblies typically have a roller mounted at an upper side of the frame around which a suitable screen is wound. The screen may be lowered and raised by rotating the roller. The lower end of the screen may be provided with a bar such that the screen hangs from the roller under gravity.
A problem with such known screen assemblies is that the width of the roller must be accurately matched to the width of the window opening to enable the screen assembly to be mounted within the window opening. Furthermore, gaps between the sides of the screen and the sides of the window opening prevent the screen from completely shutting out light when the screen is closed.